1. Field of the Invention
The present invention generally relates to a non-volatile memory and method of manufacturing the same, and more particularly, to a non-volatile memory with protective block structures for preventing conventional pitting issue and method of manufacturing the same.
2. Description of the Prior Art
A non-volatile memory, such as flash or EEPROM, retains stored data even if power to the memory is removed. A non-volatile memory cell stores data, for example, by storing electrical charge in an electrically isolated memory gate or in a charge-trapping layer underlying a control gate of a field-effect transistor (FET). The stored electrical charge controls the threshold of the FET, thereby controlling the memory state of the cell. A non-volatile memory cell is programmed using, for example, hot carrier injection to place charge into a storage layer. High drain and gate voltages are used to facilitate the programming process, and the memory cell conducts relatively high current during programming, which can be undesirable in low voltage or low power applications.
In common non-volatile memory manufacturing processes, the memory gates in memory area (cell) and the logic gates in logic area are usually defined/formed in different steps since the devices in two areas have different components and functionality. The memory gates are usually defined before the logic gates. This step configuration makes the memory devices have high risk to be damaged in the following logic process. The damage issue, which is commonly referred as pitting issue by those ordinarily skilled in the art, is found mainly between memory gates in tight cell area where the hard mask may not properly and uniformly cover and protect the substrate. The poorly-covered substrate between the tightly-spaced memory gates may be easily damaged by following process, such as the poly-Si etching process for forming the logic gates. This pitting issue may impact the overall electrical performance. Accordingly, there is a need for a novel design for non-volatile memory device and methods for preventing the pitting issue in the process in order to improve the performance and reliability of the memory device.